1. Technical Field
The present invention relates to a piezoelectric device having a piezoelectric element on a substrate, an inspection method for a piezoelectric device, and a liquid ejecting head including a piezoelectric device.
2. Related Art
A piezoelectric element is formed by interposing a piezoelectric material having an electromechanical conversion function, for example, a piezoelectric layer formed of a crystallized dielectric material, between two electrodes. To measure displacement of this piezoelectric element, it has been suggested to perform an evaluation of the piezoelectric element by forming a test pattern on a substrate and measuring the displacement of the test pattern (for example, refer to JP-A-2010-87102). In addition, it has been suggested that by measuring the resistance of one of the electrodes of the piezoelectric element, as a test pattern, a thickness thereof can be measured (for example, refer to JP-A-2008-124343).
Here, in a piezoelectric element, although electrical characteristics affects characteristics of the piezoelectric element, the main factors for determining the electrical characteristics include the crystal structure, film thickness, film composition, and film density of the piezoelectric layer. Although these characteristics can be measured using mainly instrumental analysis in which optical inspection by X-ray is performed, as in JP-A-2010-87102 and JP-A-2008-124343, there is a problem in that the characteristics cannot be measured in a configuration in which an electrode is disposed in a portion to be measured.
Even though the piezoelectric layer is measured after forming the piezoelectric layer on one of the electrodes, when forming the other electrode on the piezoelectric layer after measuring, the piezoelectric layer sustains damage. Therefore, damage due to a post-processing of the piezoelectric layer is not reflected in the measurement result, and there is a variation in characteristics between the measurement result and the actual piezoelectric layer which becomes the piezoelectric element. Accordingly, there is a problem in that the piezoelectric layer cannot be evaluated with high precision.
Therefore, although it is conceivable to have an inspection region on a portion that is not a product region of the substrate on which the piezoelectric element is formed, if there is a distance between the product region and the inspection region, a difference between the piezoelectric layer of each product region and the measurement result of the inspection region occurs due to variations in manufacturing. Accordingly, there is a problem in that the actual piezoelectric layer of the product region cannot be evaluated with high precision.
Such problems are not limited to a piezoelectric device used in a liquid ejecting head or the like represented by an ink jet recording head and are similarly present in other piezoelectric devices.